Electrical insulator links



Feb. 9, 1960 J. E. cox

ELECTRICAL INSULATOR LINKS Filed April 20, 1953 United States Patent 0.ELE'C'IRICAL-INSULATOR LINKS John Edward'Cox, Melbourne, Victoria,Australia Application April 20, 1953, Serial No. 349,710

2 Claims. (Cl. v174179) This invention relates to high-tension electricinsulators, andis concerned with theconstruction of jointsbetweencomponent parts of such insulators and between the insulator and itssupport, and in cases in which the. insulator suports an electricconductor, of'the joints-ibetweenthe insulator and such conductor. Theinventionisparticularly applicable to high tension insulators subjectedto mechanical load ortension, such as the links of a: high tensioninsulator chain and to insulating bushings, such as bushings fortransformer tanks or, in general, bushings which have to take conductorsthrough a wall or partition with a gas-, wateror oil-tight joint.Hitherto such joints have usually been made by'employing cement betweenthe insulator and acomponent part, often with a cushion between them,such as a layer of bitumen or hemp or a keying of glazed porcelainparticles. Metal parts have also been secured to insulatorsby moltenlead or other soft metal, and in joining the components of multi-partinsulators more than one ofthe above methods are sometimes usedincombination.

The object of the present invention is to provide a simple and reliablejoint for the above purposes, which can be made liquidor gas-tight and,as already indicated, can be applied to insulators which havetobe'subjected to considerable mechanical tension.

Thus, according to the present invention, the joint between the twoparts to be connected-whether it is to be between metal and insulatororinsulator and insulatoris formed by one or more'resilient rings ofyielding material, such as natural rubber, synthetic rubber particularlyneoprene, thermoplastic. synthetic resin and so forth. The ring isinserted between the two parts to be joined which are made to fitWelltogether in telescoping relation so the ring or rings when inposition is compressed between the two closely-spaced surfaces and formsthe-necessary joint. The ring, or rings, is seated in oneor more annulargrooves formed in one of the cooperatingsurfaces of the parts to bejoined. The provision of'such grooves serves definitely to locate therings and to prevent them being displaced, and also ensures that thedistortion of the rings is localized to make a goodjoint by being firmlypressed into the narrow gap between the cooperating surfaces.

In the case of an insulator to be placed under tension, for example alink of an insulator chain, the tension member is secured to a metalterminalat either end and is enclosed in an insulating housing, such asa glass or porcelain tube. The terminal members may have outer sleeveswhich make joint-with the insulating housing in accordance with theinvention, for example by the use of rings located in grooves in thesesleeves of the terminals. Also, at one or both ends, the terminals mayhave an inner surface which makes joint with the inner tension memberalso by means of one or more of the yielding rings.

Also, in the case of transformer bushings or like structures for indooror outdoor use, the joint at either end between the conductor and theinsulator may be made with metal members which have an inner surfacemaking joint with the conductor and a sleeve engaging outside theinsulatonthe joint being made in both cases in accordance with theinvention, by one or more yielding rings. In the case of a tank bushing,a metal member secured to the coveror wall of the tank may also have aninner cylindrical surface which makes joint with the insulator by one ormore rings in accordance with the invention as already indicated.

In order to'illustrate the invention in more detail, some examplesthereof will now be described more fully with reference to theaccompanying drawings, in which:

Figure 1 is an axial longitudinal section of a link for a high tensioninsulator chain;

Figure 2is a transverse section on the line 11-11 in Figure 1;

Figure 3 is an axial section showing a modification of the attachment ofthe link as an alternative to that at the lower end of Figure 1, and

Figure 4 is a longitudinal axial section of a transformer bushing inaccordance with the invention.

Referring first of all to Figures 1 and 2, in this case the internaltension member 1 consists of a rod of wood which has been impregnatedwith a synthetic resin forced under pressure into thepores of the wood.This material may be beech wood impregnated with an insolublephenolformaldehyde resin, such as the material known in the trade asPermali. It has a somewhat octagonal section along its main length, butat each end has a circular part 2 arranged to be-screw-threaded into theterminal member or socket 3, 4 and secured by pins 5. The upper member 3is formed at its outer end with a socket 6 of a ball joint intended toreceive the head 7 of the adjacent link. The terminal 3 is convenientlymade as a malleable iron casting and galvanized.

The lower terminal member 4 which bears the head 7 may be a mild steelforging, and as it has to make joint with a cap 8 and requires anaccurate outer surface, it may be cadmiurn plated.

Since the tension member 1 has to sustain considerable tension, theterminal members 3, 4 have relatively long inwardly extending socketsinto which the cylindrical ends 2 of the members 3, 4 arescrew-threaded. The outer housing or container is, in this case, a glasstube 9 with a fairly accurate outer surface which, at the upper end,

is enclosed by the outer sleeve 10 of the terminal member -3. At thelower'or head end of the link, the cap 8 also has a sleeve 11 engagingthe outer surface of the glass tube 9, and this cap may conveniently bemade of aluminum. Thus, the outer sleeve 11 andthe inner member 12 ofthe cap 8 which haveto'make joint respectively with the outer surface ofthe glass tube 9 and the stem 13 of the terminal member 4, are eachformed with two shallow annular grooves in each of which is lodged aresilient ring 14, '15 which, in this example, is of neoprene. The ringsstand out from their grooves so as to be compressed when the cap 8 isfitted 'over the glass tube 9 on the one'handand'the stem 13 on theother. It isimportant to formthe glass tube 9 with a bevelled orchamfered part 16 at either end, and toform the stem 13 with a chamferedpart 17'to aflord an easy entry of the tube 9 and stem '13 into thegrooved surfaces of the cap 8, so that whenthe cap slides on to thesetwo members, oil-tight'joints'areformed by the rings 14, I5.

Atthe'upperorsocket end, the terminal "3, .as already mentioned,.is inone piece with the socket 6 and, in .this case also, two grooves areformed on the inner surface of the sleeve 10 to receive similarresilient rings 18 which thus make joint between the terminal member 3and the outside of the glass tube 9.

It is possible to provide a filling hole for filling the glass casing 9with good quality insulating oil, but this is not necessary in theconstruction shown because the unit may be filled with oil or inertpowder during assembly as follows: The rod 1 is screwed into the socketof the terminal member 3;. the rings .18 are placed in their grooves andthe glass. tube 9 at its upper end inserted into the sleeve 10, thechamfer 16 assisting. in this without disturbing the rings 18. Then withall the parts in position except the lower terminal cap 8, the casing 9is filled with oil while the unit is inverted in relation to Figure 1 ofthe drawings and, finally, the terminal cap 8 with the rings 14 and 15in position is caused to slide on to the glass tube 9 and the stem 13 ofthe terminal 4.

In experiments made with a link constructed as above in which thescrew-threaded ends of the rod 1 were about 1.4 inches in diameter, itwas found that the flash-over voltage was about 160 kilovolts and thecorona. level about 150 kilovolts. Thus the corona level is very muchhigher in relation to the flash-over voltage than is usual in otherforms of insulator links.

Other forms of terminal members may obviously be used with the samegeneral internal construction. Thus, if an insulator of thisconstruction is to be used in compression, for example for supporting aradio tower, the terminal members 3 and 4 would then be shaped at theirupper ends with flat discs or flanges suitable for seating on a suitablesurface.

Sometimes, from the point of view of mechanical strength, it isdesirable to fit such a device with clevis terminal members. In the caseof the upper teiminal shown in Figure 1, it is only a question ofcasting the terminal member 3 with the central member of a clevis or afork. However, at the lower end of Figure l, the construction needs somemore modification and an example of this is shown in Figure 3. In thisfigure the lower end of the glass tube 9 and the screw-threaded end 2 ofthe rod 1 are shown as well as the lower terminal member 4. However, theextreme lower end of the member 4v is now shaped somewhat differently,being bored at the bottom and tapped to receive the screw-threaded stemof the fork or clevis 19 which is screwed into the member 4 and issecured by a pin 20. The sealing member 8a which serves the same purposeas the member 8 in Figure 1 is now of somewhat different shape. It makesa joint with the glass tube 9 by a pair of rings 14a as in Figure 1, butinstead of being turned inwardly it is formed with a downward extensionto make joint with the stem 13 of the member 4. In this case, however,joint rings 15a are lodged in grooves in the stem 13 and not in themember 8a. As a matter of fact at all of the joints shown in Figures 1and 3 the grooves could be made in the opposite member except, ofcourse, that it is not very convenient to form annular grooves in theglass tube 9.

In Figure 4 which shows the invention applied to a transformer bushing,joints which are gas-, waterand oil-tight have to be made between theporcelain insulator 21 and the conductor 22 of the bushing both outsideand inside the transformer tank, the cover of which is indicated at 23.Also a similar joint has to be made between the insulator 21 and thecover 23. At the outside of the tank, there is a jointing member 24consisting of a non-ferrous casting formed with internal annular groovesto receive one pair of the yielding rings 25 which make joint with theconductor 22, and another pair of rings 26 which make joint with theoutside surface of the insulator 21 in much the same way as in Figure 1.A similar non-ferrous casting 27 is used inside the tank and formed withgrooves to receive one pair of yielding rings 28 for making joint withthe conductor 22, and to receive another pair of rings 29 making jointwith the outside of the insulator 21 exactly at the top. In order tomake joint with the tank cover 23 a flanged member 30 is secured bybolts 31 to the cover 23 and has a pair of annular grooves to receive apair of yielding rings 32 for making joint with the outside of theinsulator 21.

The insulator 21 is shown with the usual sheds 33. In Figures 1 and 3the glass tube 9 is shown with a smooth outer surface but it may beprovided with sheds to increase the creepage path along it, and alsoeither or both of the end members 10, 11, may, if desired, be formedwith inclined rain sheds.

I claim:

1. A high tension electric insulator link comprising an insulatingelongated tension member comprising an insulating rod, an insulatingtubular housing surrounding said tension member, a terminal member ateach end of said tension rod the end portions of which are threaded intosaid terminal members, at least one of said terminal members beingformed as a cap and with a skirt closely embracing the end of saidhousing and the cylindrical engaging surface of at least said housing orsaid cap being formed with an annular groove and a yielding jointingannular gasket housed in said groove and dimensioned so as to becompressed between the closelyspaced surfaces of said housing and saidcap upon said housing and said cap being telescoped together, saidgasket also being dimensioned so as to fill completely said groove aftersaid housing and cap have been forced together and being substantiallycompletely confined be tween said housing and the skirt of said cap.

2. A high tension electric insulator link comprising an" insulatingelongated tension member, an insulating tubular housing surrounding saidtension member, a terminal member at each end of said tension member andsecured to the latter, said terminal member at one end being formed as acylindrical stem and said terminal member at the other end being formedas a cap and with a skirt closely embracing the end of said housing, asecond 'cap formed with a skirt embracing the opposite end of saidhousing and with a sleeve closely embracing said first mentionedterminal member, each of said skirts and said sleeve being formed with apair of annular grooves on their inner surfaces and a plurality of pairsof yielding jointing annular gaskets housed in said grooves andrespectively dimensioned so as to be compressed between theclosely-spaced surfaces of each of said skirts and said housing and ofsaid sleeve and said cylindrical stem upon said respective parts beingtelescoped together.

References Cited in the file of this patent UNITED STATES PATENTS1,876,581 Austin Sept. 13, 1932 1,983,335 Austin Dec. 4, 1934 2,284,530Meyer May 26, 1942 2,429,426 Phillips et al. Oct. 21, 1947 2,443,545Schwennesen June 15, 1948 2,452,580 Lee Nov. 2, 1948 2,552,686 MelcherMay 15, 1951* FOREIGN PATENTS 25,613 France Apr. 21, 1923 (1st additionto 540,916)

OTHER REFERENCES Publication: Parker O-Rings and Special Seals, TheParker Appliance Company, Catalog 903, October 1950, page 42.

